Carrier pipes such as those used in water distribution systems are typically located underground and subjected to significant dynamic and static loads, corrosive elements, vibrations, and other destructive factors, particularly when located under roads and railway rights-of-way. As a result, these types of pipelines are frequently in the form of an inner liquid carrying pipe disposed within a rigid outer casing. The outer casing isolates the inner pipe from the elements as well as from ground movement and the structural stresses associated therewith. One or more carrier pipes may be disposed within the outer casing, where the inner carrier pipe(s) may be a water or sewer main. The outer casing serves to maintain carrier pipe alignment, restrain the carrier pipe against flotation or other movement, and maintain the carrier pipe in fixed position and orientation, such as for maintaining grade requirements in the case of a gravity sewer. One or more spacers are typically disposed about the carrier pipe(s) and between the carrier pipe(s) and the outer casing to maintain stationary positioning and fixed spacing of the carrier pipe(s) relative to the outer casing.
Early casing spacers made use of suitably sized lumber banded about selected portions of the carrier pipe before it is placed within the outer casing. The lumber tends to degrade over time and is subject to damage or destruction during installation. These wooden spacers are labor intensive to fabricate and attach to a carrier pipe and are positioned within an outer casing in a manner which tends to increase the possibility of damage or destruction of the casing spacer. These types of wooden spacers are also easily dislodged from the carrier pipe such as during installation and place an uneven load on the pipe unless the boards are spaced symmetrically about the inner carrier pipe. These wooden spacers are also subject to rot, allowing the carrier pipe to settle, or they can, on the other hand, swell and subject carrier pipe joints to breakage. These wooden spacers also provide only limited electrical insulation for the carrier pipe, and are subject to bacterial and differential oxygen concentration corrosion.
More recent casing spacer designs feature a preformed steel or plastic band tightly maintained in position about the outer surface of the carrier pipe. Attached to and extending from the outer surface of the casing spacer band are plural spaced risers. In the case of a steel casing spacer band, the risers are also comprised of steel and are attached to the casing spacer band by conventional means such as weldments. In the case of a plastic casing spacer band, the risers are also of plastic and are integrally formed with the band. A riser/runner arrangement disposed about the outer surface of the casing spacer's band provides this arrangement with a cross sectional shape generally in the shape of a “star”. While the risers disposed on the outer surface of the casing spacer provide considerable strength in supporting a carrier pipe within the casing, this component substantially increases the cost and complexity of manufacture because it must be attached to the casing spacer's band in a separate step. Forming the riser integrally with the casing spacer band during manufacture also substantially increases the cost and complexity of casing spacer manufacture. Other casing spacer designs have eliminated the use of a riser by bolting the runners to the casing spacer's bands. These mounting bolts are attached to the casing spacer's bands by means of stud weldments. These stud weldments, as in the case of the aforementioned riser weldments, increase the complexity and cost of casing spacer manufacture. Once installed, the stud weldments are also subject to failure when subjected to the significant dynamic and static loads encountered in underground environments.
The present invention addresses the aforementioned limitations of the prior art by providing a casing spacer for maintaining a carrier pipe in spaced position within, and from, an outer casing which does not make use of risers or weldments for positioning and support of the carrier pipe. Plural runners are securely attached in a spaced manner directly to the outer surface of the casing spacer band in a novel mounted arrangement which eliminates the need for risers or weldments. The inventive riserless casing spacer is easily assembled and attached to a carrier pipe, is of reduced complexity and low cost, and provides secure support for a carrier pipe disposed within an outer casing.